FUNCTIONS OF THE SALIVA. 213 



ment of taking a little cooked starch into the mouth, mixing it well with the saliva, and 

 testing in the ordinary way for sugar. This can hardly be done so rapidly that the reac- 

 tion is not manifested, and the presence of sugar is also indicated by the taste. Although 

 the human mixed saliva will finally exert the same action on uncooked starch, the trans- 

 formation takes place much more slowly. It has been shown by experiment that all the 

 varieties of human saliva have the same effect on starch as the mixed fluids of the mouth. 

 Dalton found no difference in the pure parotid saliva and the mixed saliva of the human 

 subject, as regards the power of transforming starch into sugar. Bernard obtained the 

 pure secretions from the parotid and from the submaxillary glands in the human subject, 

 by drawing it out of the ducts, as they open into the mouth, with a small syringe with 

 the nozzle arranged so as to fit over the papillae, and demonstrated their action on starch. 

 Longet showed that a mixture of the secretions of the submaxillary and the sublingual 

 glands had the same property. 



It is unnecessary, in this connection, to recite the numerous experiments on the in- 

 fluence of the saliva of the inferior animals on starch; but it may be stated, as an estab- 

 lished and generally-accepted fact, that the mixed saliva and the secretion of the different 

 salivary glands, in the human subject, invariably transform cooked starch into sugar with 

 great rapidity in the mouth, and also, at the proper temperature, out of the body. It 

 has been also shown by Mialhe that the starch, although it is converted rapidly into sugar 

 in this process, is first transformed into dextrine. This point being settled, there arises 

 the important question whether the action of the saliva be important in the digestion of 

 starch, or whether this transformation be merely accidental; for it has been shown that 

 other fluids, among which may be mentioned the serum of the blood, the fluid found in 

 cysts, and mucus, have the same property, although none, except the intestinal juices, are 

 nearly so efficient as the saliva. And, again, the quantity of starch contained in the food 

 is so great that it would require, apparently, a longer contact with the saliva than usually 

 takes place in the mouth to make this action very efficient. These considerations make 

 it necessary to follow the amylaceous principles of food into the stomach and to ascer- 

 tain, if possible, whether the transformation into sugar be continued in this organ. 



Bernard, after feeding a dog with starch, drew off the contents of the stomach by a 

 gastric fistula and found the starch unchanged, with no traces of sugar. This experi- 

 ment we have often repeated in public demonstrations, with the same results ; but the 

 differences already noted in the properties of the saliva of the human subject and of the 

 inferior animals destroy much of the value of such observations. Longet and others have 

 shown that the addition of gastric juice to the saliva does not interfere with the action 

 of the latter on starch, but it has been found that the reaction of the sugar thus resulting 

 from the transformation of the starch is masked by the presence of other principles con- 

 tained in the stomach. The question of the continuance, in the stomach, of the digestion 

 of starch by the saliva is settled by the following observation by Grtinewaldt and 

 Schroder, in 1853, on a woman with a gastric fistula: 



"After a meal of raw starch, no sugar was found in the contents of the stomach, the 

 acid juice was drawn by the fistula, and was mixed with paste ; the transformation into 

 sugar commenced immediately. As Bidder has observed, the transforming property of 

 the saliva persists, even in the presence of free acids. 



"A few ounces of starch swelled with boiling water were introduced in the stomach, 

 fasting, by the fistula; immediately after, a portion of the starch was expelled again; 

 already it contained sugar. A quarter of an hour after, a great deal of sugar was found 

 in the stomach, and the paste had become entirely fluid." 



There can be no doubt that the saliva, in addition to its important mechanical func- 

 tions, transforms a considerable portion of the cooked starch, which is the common form 

 in which this principle is taken by the human subject, into sugar; but it is by no means 

 the only fluid engaged in its digestion, similar properties belonging, as we shall see here- 

 after, to the pancreatic and the intestinal juice. The last-named fluids are probably more 



